[fomine3]

I don't know other languages/VMs that requires to set JVM's Xmx/Xms equivalent parameter. Why only JVM requires it? What about to just set unlimited by default?

[winrid]

Generally, you want to leave some memory available to other things, like the OS, buffers in the network stack, etc.

Having a limit for the VM is helpful. Also, by default it is automatically 20% of available memory.

Personally, I've had to tune this kind of stuff with every VM I worked with (JVM, Node, PHP). :)